Multi-mode starter-generator device transmission with single valve control

ABSTRACT

A power control system is provided for a work vehicle with an engine. A combination starter-generator device has an electric machine and a gear set configured to receive rotational input from the electric machine and the engine and to couple the electric machine and the engine in two power flow directions. The gear set operates in one of multiple relatively high-torque, low-speed start gear ratios in one direction, including a first start gear ratio corresponding to a cold engine start mode and a second start gear ratio corresponding to a warm engine start mode, and in a relatively low-torque, high-speed gear ratio in another direction corresponding to a generation mode. First and second clutch assemblies are selectively coupled to the gear set to effect the start gear ratios during the engine start modes. A control valve is fluidly coupled to selectively apply a fluid pressure to the clutch assemblies.

CROSS-REFERENCE TO RELATED APPLICATION(S)

Not applicable.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE DISCLOSURE

This disclosure relates to work vehicle power systems, includingarrangements for starting mechanical power equipment and generatingelectric power therefrom.

BACKGROUND OF THE DISCLOSURE

Work vehicles, such as those used in the agriculture, construction andforestry industries, and other conventional vehicles may be powered byan internal combustion engine (e.g., a diesel engine), although it isbecoming more common for mixed power sources (e.g., engines and electricmotors) to be employed. In any case, engines remain the primary powersources of work vehicles and require mechanical input from a starter toinitiate rotation of the crankshaft and reciprocation of the pistonswithin the cylinders. Torque demands for starting an engine are high,particularly so for large diesel engines common in heavy-duty machines.

Work vehicles additionally include subsystems that require electricpower. To power these subsystems of the work vehicle, a portion of theengine power may be harnessed using an alternator or generator togenerate AC or DC power. The battery of the work vehicle is then chargedby inverting the current from the alternator. Conventionally, a belt,direct or serpentine, couples an output shaft of the engine to thealternator to generate the AC power. Torque demands for generatingcurrent from the running engine are significantly lower than for enginestart-up. In order to appropriately transfer power between the engineand battery to both start the engine and generate electric power, anumber of different components and devices are typically required,thereby raising issues with respect to size, cost, and complexity.

SUMMARY OF THE DISCLOSURE

This disclosure provides a combined engine starter and electric powergenerator device with an integral transmission, such as may be used inwork vehicles for engine cold start and to generate electric power, thusserving the dual purposes of an engine starter and an alternator withmore robust power transmission to and from the engine in both cases.

In one aspect the disclosure provides a combination starter-generatorfor a work vehicle having an engine that includes an electric machineand a gear set configured to receive rotational input from the electricmachine and from the engine. [claims].

In another aspect the disclosure provides a drivetrain assemblyincluding an engine, an electric machine, and a gear set configured toreceive rotational input from the electric machine and from the engine.[claims].

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features and advantages willbecome apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of an example work vehicle in the formof an agricultural tractor in which the disclosed integratedstarter-generator device may be used;

FIG. 2 is a simplified partial isometric view of an engine of the workvehicle of FIG. 1 showing an example mounting location for an examplestarter-generator device;

FIG. 3 is a schematic diagram of a portion of a power transferarrangement of the work vehicle of FIG. 1 having an examplestarter-generator device;

FIG. 4 is a cross-sectional view of a power transmission assembly of theexample starter-generator device that may be implemented in the workvehicle of FIG. 1;

FIG. 5 is a more detailed view of a portion of the power transmissionassembly of FIG. 4 for the example starter-generator device;

FIG. 6 is a sectional view of the power transmission assembly of FIG. 4depicting a schematic representation of a power flow path in a firstengine start mode of the example starter-generator device;

FIG. 7 is a sectional view of the power transmission assembly of FIG. 4depicting a schematic representation of a power flow path in a secondengine start mode of the example starter-generator device;

FIG. 8 is a sectional view of the power transmission assembly of FIG. 4depicting a schematic representation of a power transfer path in ageneration mode of the example starter-generator device;

FIG. 9 is a cross-sectional view of a further example power transmissionassembly of the example starter-generator device that may be implementedin the work vehicle of FIG. 1;

FIGS. 10 and 11 are more detailed views of a portion of the powertransmission assembly of FIG. 9 for the example starter-generatordevice;

FIG. 12 is a graph depicting the relationship between control valvepressure, clutch torque capacity, and output torque during engine startmodes of the power transmission assembly of FIG. 9;

FIG. 13 is a further more detailed view of a portion of the powertransmission assembly of FIG. 9 for the example starter-generatordevice; and

FIG. 14 is a graph depicting the relationship between control valvepressure, clutch torque capacity, and output torque during a generationmode of the power transmission assembly of FIG. 9.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

The following describes one or more example embodiments of the disclosedstarter-generator device, as shown in the accompanying figures of thedrawings described briefly above. Various modifications to the exampleembodiments may be contemplated by one of skill in the art.

As used herein, unless otherwise limited or modified, lists withelements that are separated by conjunctive terms (e.g., “and”) and thatare also preceded by the phrase “one or more of” or “at least one of”indicate configurations or arrangements that potentially includeindividual elements of the list, or any combination thereof. Forexample, “at least one of A, B, and C” or “one or more of A, B, and C”indicates the possibilities of only A, only B, only C, or anycombination of two or more of A, B, and C (e.g., A and B; B and C; A andC; or A, B, and C).

As used herein, the term “axial” refers to a dimension that is generallyparallel to an axis of rotation, axis of symmetry, or centerline of acomponent or components. For example, in a cylinder or disc with acenterline and opposite, generally circular ends or faces, the “axial”dimension may refer to the dimension that generally extends in parallelto the centerline between the opposite ends or faces. In certaininstances, the term “axial” may be utilized with respect to componentsthat are not cylindrical (or otherwise radially symmetric). For example,the “axial” dimension for a rectangular housing containing a rotatingshaft may be viewed as a dimension that is generally in parallel withthe rotational axis of the shaft. Furthermore, the term “radially” asused herein may refer to a dimension or a relationship of componentswith respect to a line extending outward from a shared centerline, axis,or similar reference, for example in a plane of a cylinder or disc thatis perpendicular to the centerline or axis. In certain instances,components may be viewed as “radially” aligned even though one or bothof the components may not be cylindrical (or otherwise radiallysymmetric). Furthermore, the terms “axial” and “radial” (and anyderivatives) may encompass directional relationships that are other thanprecisely aligned with (e.g., oblique to) the true axial and radialdimensions, provided the relationship is predominately in the respectivenominal axial or radial dimension.

Many conventional vehicle power systems include an internal combustionengine and/or one or more batteries (or other chemical power source)that power various components and subsystems of the vehicle. In certainelectric vehicles, a bank of batteries powers the entire vehicleincluding the drive wheels to impart motion to the vehicle. In hybridgas and electric vehicles, the motive force may alternate between engineand electric motor power, or the engine power may be supplemented byelectric motor power. In still other conventional vehicles, the electricpower system is used to initiate engine start up and to run thenon-drive electric systems of the vehicle. In the latter case, thevehicle typically has a starter motor that is powered by the vehiclebattery to turn the engine crankshaft to move the pistons within thecylinders. In further scenarios, the electric power system may provide aboost to an operating engine.

Some engines (e.g., diesel engines) initiate combustion by compressionof the fuel, while other engines rely on a spark generator (e.g., sparkplug), which is powered by the battery. Once the engine is operating ata sufficient speed, the power system may harvest the engine power topower the electric system as well as to charge the battery. Typically,this power harvesting is performed with an alternator or other type ofpower generator. The alternator converts alternating current (AC) powerto direct current (DC) power usable by the battery and vehicle electriccomponents by passing the AC power through an inverter (e.g., dioderectifier). Conventional alternators harness power from the engine bycoupling a rotor of the alternator to an output shaft of the engine (ora component coupled thereto). Historically this was accomplished by theuse of a dedicated belt, but in some more modern vehicles the alternatoris one of several devices that are coupled to (and thus powered by) theengine via a single “serpentine” belt.

In certain applications, such as in certain heavy-duty machinery andwork vehicles, it may be disadvantageous to have a conventional set-upwith separate starter and generator components. Such separate componentsrequire separate housings, which may require separate sealing orshielding from the work environment and/or occupy separate positionswithin the limited space of the engine compartment. Other enginecompartment layout complexities may arise as well.

The following describes one or more example implementations of animproved vehicle power system that addresses one or more of these (orother) matters with conventional systems. In one aspect, the disclosedsystem includes a combination or integrated device that performs theengine cranking function of a starter motor and the electric powergenerating function of a generator. The device is referred to herein asan integrated starter-generator device (“ISG” or “starter-generator”).This terminology is used herein, at least in some implementations of thesystem, to be agnostic to the type of power (i.e., AC or DC current)generated by the device. In some implementations, the starter-generatordevice may function to generate electricity in a manner of what personsof skill in the art may consider a “generator” device that produces DCcurrent directly. However, as used herein, the term “generator” shallmean producing electric power of static or alternating polarity (i.e.,AC or DC). Thus, in a special case of the starter-generator device, theelectric power generating functionality is akin to that of aconventional alternator, and it generates AC power that is subsequentlyrectified to DC power, either internally or externally to thestarter-generator device.

In certain embodiments, the starter-generator device may include adirect mechanical power coupling to the engine that avoids the use ofbelts between the engine and the starter-generator device. For example,the starter-generator device may include within its housing a powertransmission assembly with a gear set that directly couples to an outputshaft of the engine. The gear set may take any of various formsincluding arrangements with enmeshing spur or other gears as well asarrangements with one or more planetary gear sets. Large gear reductionratios may be achieved by the transmission assembly such that a singleelectric machine (i.e., motor or generator) may be used and operated atsuitable speeds for one or more types of engine start up, as well aselectric power generation. The direct power coupling between thestarter-generator device and engine may increase system reliability,cold starting performance, and electric power generation of the system.

Further, in certain embodiments, the starter-generator device may have apower transmission assembly that automatically and/or selectively shiftsgear ratios (i.e., shifts between power flow paths having different gearratios). By way of example, the transmission assembly may include one ormore passive engagement components that engage or disengageautomatically when driven in particular directions and/or one or moreactive engagement components that are commanded to engage or disengage.For example, passive engagement components, such as a one-way clutch(e.g., a roller or sprag clutch), may be used to effect powertransmission through a power flow path in the engine start up direction;and active engagement components, such as friction clutch assemblies,may be used to effect power transmission through other power flow paths.In this manner, bi-directional or other clutch (or other) configurationsmay be employed to carry out the cranking and generating functions withthe appropriate control hardware. As a result of the bi-directionalnature of the power transmission assembly, the power transfer beltarrangement may be implemented with only a single belt tensioner,thereby providing a relatively compact and simple assembly. In additionto providing torque in two different power flow directions, the gear setmay also be configured and arranged to provide power transmission fromthe electric machine to the engine at one of two different speeds, e.g.,according to different gear ratios. The selection of speed may provideadditional functionality and flexibility for the power transmissionassembly. For example, a lower speed or “first start” gear ratio may beprovided to facilitate cold engine starts and a higher speed “secondstart” gear ratio may be provided to facilitate warm engine starts (orengine boost).

Control of the power transmission assembly with respect to the activeclutch assemblies may take various forms. In one example, separate anddedicated control valves may be utilized to individually operate twoactive clutch assemblies. In further examples, a single control valvemay be utilized to operate both clutch assemblies to perform thedesignated functions. Each implementation will be discussed in greaterdetail below.

Referring to the drawings, an example work vehicle power system as adrivetrain assembly will be described in detail. As will become apparentfrom the discussion herein, the disclosed system may be usedadvantageously in a variety of settings and with a variety of machinery.For example, referring now to FIG. 1, the power system (or drivetrainassembly) 110 may be included in a work vehicle 100, which is depictedas an agricultural tractor. It will be understood, however, that otherconfigurations may be possible, including configurations with workvehicle 100 as a different kind of tractor, or as a work vehicle usedfor other aspects of the agriculture industry or for the constructionand forestry industries (e.g., a harvester, a log skidder, a motorgrader, and so on). It will further be understood that aspects of thepower system 110 may also be used in non-work vehicles and non-vehicleapplications (e.g., fixed-location installations).

Briefly, the work vehicle 100 has a main frame or chassis 102 supportedby ground-engaging wheels 104, at least the front wheels of which aresteerable. The chassis 102 supports the power system (or plant) 110 andan operator cabin 108 in which operator interface and controls (e.g.,various joysticks, switches levers, buttons, touchscreens, keyboards,speakers and microphones associated with a speech recognition system)are provided.

As schematically shown, the power system 110 includes an engine 120, anintegrated starter-generator device 130, a battery 140, and a controller150. The engine 120 may be an internal combustion engine or othersuitable power source that is suitably coupled to propel the workvehicle 100 via the wheels 104, either autonomously or based on commandsfrom an operator. The battery 140 may represent any one or more suitableenergy storage devices that may be used to provide electric power tovarious systems of the work vehicle 100.

The starter-generator device 130 couples the engine 120 to the battery140 such that the engine 120 and battery 140 may selectively interact inat least three modes. In a first (or cold) engine start mode, thestarter-generator device 130 converts electric power from the battery140 into mechanical power to drive the engine 120 at a relatively highspeed, e.g., during a relatively cold engine start up. In a second (orwarm) engine start (or boost) mode, the starter-generator device 130converts electric power from the battery 140 into mechanical power todrive the engine 120 at a relatively low speed, e.g., during arelatively warm engine start up (or to provide an engine boost). In athird or generation mode, the starter-generator device 130 convertsmechanical power from the engine 120 into electric power to charge thebattery 140. Additional details regarding operation of thestarter-generator device 130 during the engine start (or boost) modesand the generation mode are provided below.

As introduced above, the controller 150 may be considered part of thepower system 110 to control various aspects of the work vehicle 100,particularly characteristics of the power system 110. The controller 150may be a work vehicle electronic controller unit (ECU) or a dedicatedcontroller. In some embodiments, the controller 150 may be configured toreceive input commands and to interface with an operator via ahuman-machine interface or operator interface (not shown) and fromvarious sensors, units, and systems onboard or remote from the workvehicle 100; and in response, the controller 150 generates one or moretypes of commands for implementation by the power system 110 and/orvarious systems of work vehicle 100.

Generally, the controller 150 may be configured as computing deviceswith associated processor devices and memory architectures, ashydraulic, electrical or electro-hydraulic controllers, or otherwise. Assuch, the controller 150 may be configured to execute variouscomputational and control functionality with respect to the power system110 (and other machinery). The controller 150 may be in electronic,hydraulic, or other communication with various other systems or devicesof the work vehicle 100. For example, the controller 150 may be inelectronic or hydraulic communication with various actuators, sensors,and other devices within (or outside of) the work vehicle 100, includingvarious devices associated with the power system 110. Generally, thecontroller 150 generates the command signals based on operator input,operational conditions, and routines and/or schedules stored in thememory. In some examples, the controller 150 may additionally oralternatively operate autonomously without input from a human operator.The controller 150 may communicate with other systems or devices(including other controllers) in various known ways, including via a CANbus (not shown), via wireless or hydraulic communication means, orotherwise.

Additionally, power system 110 and/or work vehicle 100 may include ahydraulic system 152 with one or more electro-hydraulic control valves(e.g., solenoid valves) that facilitate hydraulic control of variousvehicle systems, particularly aspects of the starter-generator device130. The hydraulic system 152 may further include various pumps, lines,hoses, conduits, tanks, and the like. The hydraulic system 152 may beelectrically activated and controlled according to signals from thecontroller 150. In one example and as discussed in greater detail below,the hydraulic system 152 may be utilized to engage and/or disengageclutch assemblies within the starter-generator device 130, e.g., byapplying and releasing hydraulic pressure based on signals from thecontroller 150. Other mechanisms for controlling such clutch assembliesmay also be provided.

In one example, the starter-generator device 130 includes a powertransmission assembly (or transmission) 132, an electric machine ormotor 134, and an inverter/rectifier device 136, each of which may beoperated according to command signals from the controller 150. The powertransmission assembly 132 enables the starter-generator device 130 tointerface with the engine 120, particularly via a crank shaft (or otherengine power transfer element) 122 of the engine 120. The powertransmission assembly 132 may include gear sets in variousconfigurations to provide suitable power flows and gear reductions, asdescribed below. The power transmission assembly 132 variably interfaceswith the electric machine 134 in two different power flow directionssuch that the electric machine 134 operates as a motor during the enginestart modes and as a generator during the generation mode. In oneexample, discussed below, the power transmission assembly 132 is coupledto the electric machine 134 via a power transfer belt arrangement. Thisarrangement, along with the multiple gear ratios provided by the powertransmission assembly 132, permit the electric machine 134 to operatewithin optimal speed and torque ranges in both power flow directions.The inverter/rectifier device 136 enables the starter-generator device130 to interface with the battery 140, such as via direct hardwiring ora vehicle power bus 142. In one example, the inverter/rectifier device136 inverts DC power from the battery 140 into AC power during theengine start modes and rectifies AC power to DC power in the generationmode. In some embodiments, the inverter/rectifier device 136 may be aseparate component instead of being incorporated into thestarter-generator device 130. Although not shown, the power system 110may also include a suitable voltage regulator, either incorporated intothe starter-generator device 130 or as a separate component.

Reference is briefly made to FIG. 2, which depicts a simplified partialisometric view of an example mounting location of the starter-generatordevice 130 relative to the engine 120. In this example, the integratedstarter-generator device 130 mounts directly and compactly to the engine120 so as not to project significantly from the engine 120 (and therebyenlarge the engine compartment space envelope) or interfere with variousplumbing lines and access points (e.g., oil tubes and fill opening andthe like). Notably, the starter-generator device 130 may generally bemounted on or near the engine 120 in a location suitable for coupling toan engine power transfer element (e.g., a crank shaft 122 as introducedin FIG. 1).

Reference is additionally made to FIG. 3, which is a simplifiedschematic diagram of a power transfer belt arrangement 200 between thepower transmission assembly 132 and electric machine 134 of thestarter-generator device 130. It should be noted that FIGS. 2 and 3depict one example physical integration or layout configuration of thestarter-generator device 130. Other arrangements may be provided.

The power transmission assembly 132 is mounted to the engine 120 and maybe supported by a reaction plate 124. As shown, the power transmissionassembly 132 includes a first power transfer element 133 that isrotatably coupled to a suitable drive element of the engine 120 (e.g.,crank 122 of FIG. 1) and a second power transfer element 135 in the formof a shaft extending on an opposite side of the power transmissionassembly 132 from the first power transfer element 133. Similarly, theelectric machine 134 is mounted on the engine 120 and includes a furtherpower transfer element 137.

The power transfer belt arrangement 200 includes a first pulley 210arranged on the second power transfer element 135 of the powertransmission assembly 132, a second pulley 220 arranged on the powertransfer element 137 of the electric machine 134, and a belt 230 thatrotatably couples the first pulley 210 to the second pulley 220 forcollective rotation. As described in greater detail below, during theengine start modes, the electric machine 134 pulls the belt 230 torotate pullies 210, 220 in a first clock direction D1 to drive the powertransmission assembly 132 (and thus the engine 120); and during thegeneration mode, the power transmission assembly 132 enables the engine120 to pull the belt 230 and rotate pullies 210, 220 in a second clockdirection D2 to drive the electric machine 134.

As a result of the bi-directional configuration, the power transfer beltarrangement 200 may include only a single belt tensioner 240 to applytension to a single side of the belt 230 in both directions D1, D2.Using a single belt tensioner 240 to tension the belt 230 isadvantageous in that it reduces parts and complexity in comparison to adesign that requires multiple belt tensioners. As described below, thebi-directional configuration and associated simplified power transferbelt arrangement 200 are enabled by the bi-directional nature of thegear set in the power transmission assembly 132. Additionally, adifference in the circumferences of the first and second pullies 210,220 provides a change in the gear ratio between the power transmissionassembly 132 and the electric machine 134. In one example, the powertransfer belt arrangement 200 may provide a gear ratio of between3:1-5:1, particularly a 4:1 ratio.

In one example, FIG. 4 depicts a cross-sectional view of the powertransmission assembly 132 that may be implemented into thestarter-generator device 130. As shown, the power transmission assembly132 may be considered to be a unit with an annular housing 302configured to house various components of the power transmissionassembly 132. The housing 302 may be fixedly mounted to the engine 120,as reflected in FIG. 2. As described below, the housing 302 may includea number of internal flanges and elements that interact with orotherwise support the internal components of the power transmissionassembly 132.

In the view of FIG. 4, a first side 304 of the housing 302 is orientedtowards the electric machine 134, and a second side 306 of the housing302 is oriented towards the engine 120. At the first side 304, the powertransmission assembly 132 includes an input shaft 310 that interfaceswith the electric machine 134 (e.g., via the power transfer beltarrangement 200). In particular, the input shaft 310 is fixed to thepower transfer element 135 described above with reference to FIGS. 1 and2. It should be noted that, although the shaft 310 is described as an“input” shaft, it may transfer power both into and out of the powertransmission assembly 132, depending on the mode, as described below.

The input shaft 310 includes a base or hub 312 that is generally hollowand centered around a primary rotational axis 300 of the powertransmission assembly 132. The input shaft 310 further includes an inputshaft flange 314 with one end generally extending in a radial directionfrom the input shaft base 312. An input shaft clutch element 316 ispositioned on the other end of the input shaft flange 314 and includesan inwardly extending set of plates 315 and an outwardly extending setof plates 317. As described in greater detail below, the input shaft 310is supported by bearings 318 to rotate relative to the housing 302.

The power transmission assembly 132 further includes a planetary gearset 320 arranged within the housing 302. As described below, the gearset 320 is a two stage planetary gear set and generally enables thepower transmission assembly 132 to interface with the electric machine134 (e.g., via the power transfer belt arrangement 200) and the engine120 (e.g., via direct coupling to the crank shaft 122 of the engine120). Although one example configuration of the gear set 320 isdescribed below, other embodiments may have different configurations.

In one example, the gear set 320 includes a first-stage sun gear 322 isformed by a shaft 324 with first and second ends 325, 326. The first end325 of the first-stage sun gear shaft 324 is oriented towards the firstside 304 of the power transmission assembly 132, and the second end 326is oriented towards the second side 306 of the power transmissionassembly 132. As described in greater detail below, a first clutchassembly 362 is splined or otherwise fixed on the first-stage sun gearshaft 324 at a position proximate to the first end 325. The second end326 of the first-stage sun gear shaft 324 includes a plurality of teethor splines that mesh with a set of first-stage planet gears 328.

In one example, the first-stage planet gears 328 include a singlecircumferential row of one or more planet gears, although otherembodiments may include radially stacked rows, each with an odd numberof planet gears. The first-stage planet gears 328 are supported by afirst-stage planet carrier 330, which circumscribes the shaft 324 of thefirst-stage sun gear 322 and is at least partially formed by first andsecond radially extending, axially facing carrier plates 332, 334. Thefirst-stage carrier plates 332, 334 include radially extending flangesthat each provides a row of mounting locations for receiving axlesextending through and supporting the first-stage planet gears 328 forrotation. As such, in this arrangement, each of the planet axlesrespectively forms an individual axis of rotation for each of thefirst-stage planet gears 328, and the first-stage planet carrier 330enables the set of first-stage planet gears 328 to collectively rotateabout the first-stage sun gear 322.

The gear set 320 further includes a ring gear 336 that circumscribes thefirst-stage sun gear 322 and the first-stage planet gears 328. The ringgear 336 includes radially interior teeth that engage the teeth of thefirst-stage planet gears 328. As such, first-stage planet gears 328extend between, and engage with, the first-stage sun gear 322 and thering gear 336.

The ring gear 336 is positioned on bearings 338 to rotate relative tothe stationary housing 302. With respect to the planetary gear set 320,the ring gear 336 may function as the power transfer element 133relative to the engine 120. In particular, the ring gear 336 includes anumber of castellations 340 that extend axially about the circumferenceof the axial face that faces the engine 120. The castellations 340engage and rotatably fix the ring gear 336 to the crank shaft 122 of theengine 120.

The gear set 320 further includes a second-stage sun gear 342 formed bya generally hollow shaft 344 that circumscribes the first-stage sun gear322 and extends between first and second ends 346, 348. The first-stageplanet carrier 330 has a splined engagement with, or is otherwise fixedto, the second-stage sun gear shaft 344 proximate to the first end 346.As described in greater detail below, a second clutch assembly 362 maybe mounted on the second-stage sun gear shaft 344 at a positionproximate to the second end 348.

Additionally, the second-stage sun gear shaft 344 may include a seriesof splines that mesh with a set of second-stage planet gears 350. Thesecond-stage planet gears 350 are supported by a second-stage planetcarrier 352 formed by first and second planet carrier plates 354, 356.The second-stage planet gears 350 are positioned to additionally engagewith the ring gear 336. The second-stage planet gears 350 each have anaxle that extends between the two carrier plates 354, 356 that enableeach planet gear 350 to rotate relative to the planet carrier 352 aboutthe respective axle. As such, the second-stage planet gears 350 arepositioned in between, and engage with each of, the second-stage sungear 342 and the ring gear 336. In some examples, each second-stageplanet gear 350 has a different number of teeth than each correspondingfirst-stage planet gear 328, while in other examples, each second-stageplanet gear 350 has the same number of teeth as each correspondingfirst-stage planet gear 328.

The second-stage planet carrier 352 may further include an annularplanet carrier hub 358 that extends in an axial direction from one ofthe planet carrier plates 356. As described in greater detail below, anoverrun (or third) clutch assembly 360 may be arranged in between thesecond-stage planet carrier hub 358 and the housing 302 that enables thesecond-stage planet carrier 352 to be fixed to the housing 302 in onerotational direction and the second-stage planet carrier 352 to rotaterelative to the housing 302 in the other rotational direction.

In addition to the overrun clutch assembly 360 and as introduced above,the gear set 320 further includes one or more clutch assemblies 362, 378that operate as torque application components that selectively engageand disengage to modify the torque transfer within the gear set 320, andthus, between the engine 120 and the electric machine 134. Althoughexample implementations of the clutch assemblies 362, 378 are describedbelow, any of various clutch configurations may be used, including, forexample, roller clutches, sprag clutches, wedge clutches, over-runningclutches, hydraulic clutches, spring clutches, and mechanical diodes.

Any suitable mechanism for engaging and disengaging the first and secondclutch assemblies 362, 378 may be provided. In one example, the firstand second clutch assemblies 362, 378 may be actively engaged ordisengaged as a result of hydraulic pressure that repositions respectiveclutch elements. In one example and schematically shown in FIG. 4, thecontroller 150 may command one or more control valves 154, 156 of thehydraulic system 152 to apply and release hydraulic pressure on theclutch assemblies 362, 378 with fluid from a fluid source. As discussedin greater detail below, the first control valve 154 is associated withthe first clutch assembly 362, and the second control valve 156 isassociated with the second clutch assembly 378. Collectively, one ormore of the control valves 154, 156, the hydraulic system 152, powertransmission assembly 132, and the controller 150 may be considered apower control system 112 that functions to implement the appropriatepower flow path between the engine 120 and the electric machine 134.

The first clutch assembly 362 is functionally positioned in between theinput shaft 310 and the first-stage sun gear 322. In a first or engagedposition, the first clutch assembly 362 functionally locks the inputshaft 310 to the first-stage sun gear 322 for collective rotation, andin a second or disengaged position, the first clutch assembly 362functionally decouples the input shaft 310 from the first-stage sun gear322 for independent rotation. In one embodiment, as discussed in greaterdetail below, the first clutch assembly 362 may be considered a “springapplied, hydraulically released” engagement and disengagement mechanism.As a result, the first clutch assembly 362 may be referenced below as a“SAHR” clutch assembly 362. Additional details about the structure andoperation of the SAHR clutch assembly 362 are provided below.

In addition to FIG. 4, reference is further made to FIG. 5, which is amore detailed view of a portion of FIG. 4. As shown, the SAHR clutchassembly 362 includes a SAHR clutch hub 364 that is mounted on andengaged for rotation with the first-stage sun gear 322. A bearingassembly 374 may be arranged between the SAHR clutch hub 364 and theinput shaft 310 to enable relative rotation. A SAHR clutch flange 366extends radially outward from the SAHR clutch hub 364 and includes a setof SAHR clutch plates 368 on a radial end. The SAHR clutch plates 368extend radially outward from the SAHR clutch flange 366 and arepositioned in an axial row so as to be interleaved between the inwardlyextending set of plates 315 of the input shaft clutch element 316.

The SAHR clutch assembly 362 further includes a SAHR clutch spring 370and a SAHR piston 372 that operate to reposition the SAHR clutchassembly 362 between the engaged position and the disengaged position.The SAHR clutch spring 370 may be arranged in any suitable position,including between the input shaft flange 314 and the SAHR clutch flange366. During operation, SAHR clutch spring 370 functions to urge the SAHRclutch assembly 362 into the engaged position such that the SAHR clutchplates 368 frictionally engage the input shaft clutch element plates 315of the input shaft clutch element 316, thereby locking the SAHR clutchassembly 362 and the first-stage sun gear 322 into rotational engagementwith the input shaft clutch element 316 and the input shaft 310.

The SAHR piston 372 is coupled to the SAHR clutch plates 368 and ispositioned relative to the input shaft clutch element 316 to form acavity 376. As schematically shown, the cavity 376 is fluidly coupled toa source of fluid pressure from the hydraulic system 152 via the firstcontrol valve 154 that selectively provides and releases fluid into andout of the cavity 376. As noted above, the first control valve 154 mayreceive command signals from the controller 150 to supply and releasefluid pressure within the cavity 376. When the control valve 156 iscommanded to supply fluid into the cavity 376, the hydraulic force onthe SAHR piston 372 functions to overcome the force of the SAHR clutchspring 370 and urge the SAHR clutch plates 368 out of engagement withthe input shaft clutch element plates 315 and into the disengagedposition. Subsequently, the controller 150 may command the first controlvalve 154 to release the hydraulic pressure such that the SAHR clutchspring 370 repositions the SAHR clutch assembly 362 back into theengaged position.

The second clutch assembly 378 is functionally positioned in between theinput shaft 310 and the second-stage sun gear 342. In a first or engagedposition, the second clutch assembly 378 functionally locks the inputshaft 310 to the second-stage sun gear 342 for collective rotation, andin a second or disengaged position, the second clutch assembly 378functionally decouples the input shaft 310 from the second-stage sungear 342 for independent rotation. In one embodiment, as discussed ingreater detail below, the second clutch assembly 378 may be considered a“hydraulically applied, spring released” engagement and disengagementmechanism. As a result, the second clutch assembly 378 may be referencedbelow as a “HASR” clutch assembly 378. Additional details about thestructure and operation of the HASR clutch assembly 378 are providedbelow.

The HASR clutch assembly 378 is formed by a HASR hub 382 that is mountedon and engaged for rotation with the second-stage sun gear 342. A HASRflange 380 extends from the HASR hub 382 and includes inwardly extendingHASR plates 384. The HASR clutch plates 384 extend radially outward fromthe HASR flange 380 and are positioned in an axial row so as to beinterleaved between the outwardly extending set of plates 317 of theinput shaft clutch element 316.

The HASR clutch assembly 378 further includes a HASR spring 386 and HASRpiston 388 that operate to reposition the HASR clutch assembly 378between an engaged position and a disengaged position. The HASR clutchspring 386 (schematically shown) may be arranged in any suitableposition, including between the input shaft clutch element 316 and theHASR clutch plates 384.

The HASR piston 388 is coupled to the HASR clutch plates 384 and ispositioned relative to the input shaft clutch element 316 to form acavity 390. As schematically shown, the cavity 376 is fluidly coupled toa second source of fluid pressure from the hydraulic system 152 via thesecond control valve 156 that selectively provides and releases fluidinto and out of the cavity 390. As noted above, the second control valve156 may receive command signals from the controller 150 to supply fluidpressure to the cavity 390. The fluid pressure in the cavity 390operates to overcome the force of the HASR clutch spring 386 and urgethe HASR clutch assembly 378 into the engaged position such that theHASR clutch plates 384 frictionally engage the input shaft clutchelement plates 317 of the input shaft clutch element 316, therebylocking the HASR clutch assembly 378 and the second-stage sun gear 342into rotational engagement with the input shaft clutch element 316 andthe input shaft 310. Generally, the HASR clutch spring 386 may have alower spring force than the SAHR clutch spring 370. In some examples,the HASR clutch spring 386 may be omitted or another arrangement may beprovided to return the HASR piston 388.

Upon release of the hydraulic pressure in the cavity 390, the HASRclutch spring 386 functions to urge the HASR clutch assembly 378 intothe disengaged position such that the HASR clutch plates 384 areseparated from the input shaft clutch element plates 315, therebyenabling mutually independent rotation of the second-stage sun gear 342and the input shaft 310.

As introduced above, the variable power flow path elements of the powertransmission assembly 132 further include the overrun clutch assembly360 arranged in between the second-stage planet carrier hub 358 and thehousing 302. The overrun clutch assembly 360 is a passive element thatenables the second-stage planet carrier 352 to be fixed to the housing302 in one rotational direction (e.g., the first clock direction D1) andthe second-stage planet carrier 352 to rotate relative to the housing302 in the other rotational direction (e.g., the second clock directionD2), as discussed in greater detail below.

As introduced above, the power transmission assembly 132 may be operatedto selectively function in one of three different modes, including: afirst or low engine start mode in which the power transmission assembly132 transfers power from the battery 140 to the engine 120 with a firststart gear ratio; a second or warm engine start mode in which the powertransmission assembly 132 transfers power from the battery 140 to theengine 120 with a second start gear ratio; and a generation mode inwhich the power transmission assembly 132 transfers power from theengine 120 to the battery 140. Comparatively, the engine start modes arerelatively low speed and relatively high torque output, and thegeneration mode is relatively high speed and relatively low torqueoutput. In some scenarios and arrangements, the warm engine start modemay also be considered a boost mode in which the power transmissionassembly 132 transfers power from the battery 140 to the engine 120 whenthe engine 120 is already operating. As such, the power transmissionassembly 132 and the power transfer belt arrangement 200 arebi-directional and have different gearing ratios to transfer power indifferent power flow directions and along different power flow paths,depending on the mode. The power flow paths in the different modes aredescribed below with reference to FIGS. 6-8 in which arrows are providedto schematically represent the flows of power.

Reference is initially made to FIG. 6, which is a cross-sectional viewof the power transmission assembly 132 similar to that of FIG. 4annotated with power flow arrows. The power flow arrows of FIG. 6particularly depict operation of the power transmission assembly 132 inthe cold engine start mode.

In the cold engine start mode, the engine 120 is initially inactive, andactivation of the ignition by an operator in the cabin 108 of the workvehicle 100 energizes the electric machine 134 to operate as a motor. Inparticular and additionally referring to FIG. 3, the electric machine134 rotates the pulley 220 in the first clock direction D1, therebydriving the belt 230 and pulley 210 in the first clock direction D1. Thepulley 210 drives the element 135, and thus the input shaft 310, in thefirst clock direction D1. In the cold engine start mode, the SAHR clutchassembly 362 is engaged and the HASR clutch assembly 378 is disengaged.Since the SAHR clutch assembly 362 is engaged, the input shaft 310 islocked for rotation with first-stage sun gear shaft 324. As such, therotation of the input shaft 310 drives rotation of the first-stage sungear 322, and in turn, rotation of the first-stage sun gear 322 drivesrotation of the first-stage planet gears 328.

The first-stage planet gears 328 drive the first-stage planet carrier330, which as noted above is splined with the second-stage sun gear 342.As a result, the first-stage planet carrier 330 drives the second-stagesun gear 342 and thus the second-stage planet gears 350 in the firstclock direction D1. Upon movement in the first clock direction D1, theoverrun clutch assembly 360 is engaged such that the second-stage planetcarrier 352 is fixed to the stationary housing 302 and prevented fromrotating.

Since the number of first-stage planet gears 328 in the power flow pathis an odd number (e.g., 1), the first-stage planet gears 328 drive thering gear 336 in the opposite direction (e.g., the second clockdirection D2) relative to the first-stage sun gear 322 rotating in thefirst clock direction D1. As noted above, the ring gear 336 functions asthe power transfer element 133 to interface with the crank shaft 122 ofthe engine 120 to drive and facilitate engine start. In effect, duringthe cold engine start mode, the power transmission assembly 132 operatesas a sun-in, ring-out configuration.

In one example, the power transmission assembly 132 provides a 15:1 gearratio in the power flow direction of the cold engine start mode. Inother embodiments, other gear ratios (e.g., 10:1-30:1) may be provided.Considering a 4:1 gear ratio from the power transfer belt arrangement200, a resulting 60:1 gear ratio (e.g., approximately 40:1 to about120:1) may be achieved for the starter-generator device 130 between theelectric machine 134 and the engine 120 during the cold engine startmode. As such, if for example the electric machine 134 is rotating at10,000 RPM, the crank shaft 122 of the engine 120 rotates at about100-150 RPM. Accordingly, the electric machine 134 may thus have normaloperating speeds with relatively lower speed and higher torque outputfor cold engine start up.

Reference is now made to FIG. 7, which is a cross-sectional view of thepower transmission assembly 132 similar to that of FIG. 4 annotated withpower flow arrows. The power flow arrows of FIG. 7 particularly depictoperation of the power transmission assembly 132 in the warm enginestart mode.

In the warm engine start mode, the engine 120 may be inactive or active.In any event, the controller 150 energizes the electric machine 134 tooperate as a motor. In particular and additionally referring to FIG. 3,the electric machine 134 rotates the pulley 220 in the first clockdirection D1, thereby driving the belt 230 and pulley 210 in the firstclock direction D1. The pulley 210 drives the element 135, and thus theinput shaft 310, in the first clock direction D1. In the warm enginestart mode, the HASR clutch assembly 378 is engaged and the SAHR clutchassembly 362 is disengaged. Since the HASR clutch assembly 378 isengaged, the input shaft 310 is locked for rotation with second-stagesun gear 342. As such, the rotation of the input shaft 310 drivesrotation of the second-stage sun gear 342, and in turn, rotation of thesecond-stage sun gear 342 drives rotation of the second-stage planetgears 350. The second-stage planet gears 350 are mounted on thesecond-stage planet carrier 352. Upon movement in the first clockdirection D1, the overrun clutch assembly 360 engages such that thesecond-stage planet carrier 352 is fixed to the stationary housing 302and prevented from rotating. Since the position of the second-stageplanet carrier 352 is locked by the overrun clutch assembly 360, therotation of second-stage planet gears 350 by the second-stage sun gear342 operates to drive the ring gear 336.

Since the number of second-stage planet gears 350 in the power flow pathis an odd number (e.g., 1) in the radial direction, the second-stageplanet gears 350 drive the ring gear 336 in the opposite direction(e.g., the second clock direction D2) relative to the second-stage sungear 342 rotating in the first clock direction D1. As noted above, thering gear 336 functions as the power transfer element 133 to interfacewith the crank shaft 122 of the engine 120 to drive and facilitateengine start. In effect, during the warm engine start mode, the powertransmission assembly 132 operates as a sun-in, ring-out configuration,albeit at a lower gear ratio as compared to the cold engine start moderesulting from using the ratio of the second-stage planet gears 350 asopposed to the compounded ratio of the first- and second-stage planetgears 328, 350.

In one example, the power transmission assembly 132 provides a 4:1 gearratio in the power flow direction of the warm engine start mode. Inother embodiments, other gear ratios (e.g., 3:1-7:1) may be provided.Considering a 4:1 gear ratio from the power transfer belt arrangement200, a resulting 16:1 gear ratio (e.g., approximately 12:1 to about28:1) may be achieved for the starter-generator device 130 between theelectric machine 134 and the engine 120 during the warm engine startmode. As such, if for example the electric machine 134 is rotating at10,000 RPM, the crank shaft 122 of the engine 120 rotates at about600-700 RPM. Accordingly, the electric machine 134 may thus have normaloperating speeds with a relatively lower speed and higher torque outputfor engine start up or boost.

Reference is made to FIG. 8, which is a partial sectionalcross-sectional view of the power transmission assembly 132 similar tothat of FIG. 4 annotated with power flow arrows. The power flow arrowsof FIG. 8 particularly depict operation of the power transmissionassembly 132 in the generation mode.

Subsequent to either or both of the engine start modes, the engine 120begins to accelerate above rotational speed provided by powertransmission assembly 132, and the electric machine 134 is commanded todecelerate and to cease providing torque to power transmission assembly132. After the engine 120 has stabilized to a sufficient speed and theelectric machine 134 has sufficiently decelerated or stopped, each ofthe SAHR and the HASR clutch assemblies 362, 378 are engaged to operatethe power transmission assembly 132 in the generation mode. In thegeneration mode, the engine 120 rotates the crank shaft 122 and powertransfer element 133 that is engaged with the ring gear 336, thusdriving the ring gear 336 in the second clock direction D2. The ringgear 336 drives the first-stage planet gears 328 and the second-stageplanet gears 350, which respectively drive the first-stage sun gear 322and the second-stage sun gear 342. In the generation mode, the overrunclutch assembly 360 is disengaged. Since the SAHR clutch assembly 362and HASR clutch assembly 378 are engaged, the rotation of thefirst-stage and second-stage sun gears 322, 342 is transferred to theinput shaft 310 via the input shaft clutch element 316. Therefore, asthe ring gear 336 rotates in the second clock direction D2, the inputshaft 310 is driven and similarly rotates in the second clock directionD2 at the same rate of rotation. As noted above, the input shaft 310 isconnected with and provides output power to the electric machine 134 inthe second clock direction D2 via the power transfer belt arrangement200. In effect, during the generation mode, the power transmissionassembly 132 operates as a ring-in, sun-out configuration.

In one example, the power transmission assembly 132 provides a 1:1 gearratio in the power flow direction of the generation mode. In otherembodiments, other gear ratios may be provided. Considering a 4:1 gearratio from the power transfer belt arrangement 200, a resulting 4:1 gearratio may be achieved for the starter-generator device 130 between theelectric machine 134 and the engine 120 during the generation mode. As aresult, the electric machine 134 may thus have normal operating speedsin both power flow directions with relatively low torque output duringpower generation.

The power transmission assembly 132 discussed above with reference toFIGS. 1-8 includes power flow paths in which the active clutchassemblies 362, 378 are actuated by dedicated control valves 154, 156.Other mechanisms may be provided.

Reference is now made to FIG. 9, which is a cross-sectional view of apower transmission assembly 400 that may be implemented into thestarter-generator device 130 according to a further embodiment.Additional reference is made to FIGS. 10-12, which are partial, moredetailed views of the power transmission assembly 400. In thisembodiment, the power transmission assembly 400 is fluidly coupled tothe hydraulic system 152 (as above) via a single control valve 158 basedon command signals from the controller 150 (as above). Collectively, oneor more of the control valve 158, the hydraulic system 152, powertransmission assembly 132, and the controller 150 may be considered apower control system 114 that functions to implement the appropriatepower flow path between the engine 120 and the electric machine 134.

Unless otherwise noted, the power transmission assembly 400 is similarto the power transmission assembly 132 discussed above. In particular,the power transmission assembly 400 includes a gear set 420 with aninput shaft 410, a first-stage sun gear 422, first-stage planet gears428, first-stage planet carrier 430, a ring gear 436, a second-stage sungear 442, second-stage planet gears 450, and second-stage planet carrier452 as above. The power transmission assembly 400 further includes anoverrun clutch 460, a first or SAHR clutch assembly 462, and a second orHASR clutch assembly 478. As above, during the cold engine start mode,the first clutch assembly 462 is engaged such that the power flows fromthe input shaft 410, through the first-stage sun gear 422, through thefirst-stage planet gears 428, and out of the ring gear 436; during thewarm engine start mode, the second clutch assembly 478 is engaged suchthat the power flows from the input shaft 410, through the second-stagesun gear 442, through the second-stage planet gears 450, and out of thering gear 436; and during the generation mode, the first and secondclutch assemblies 462, 478 are engaged such that the power flows fromthe ring gear 436, through the first-stage and second-stage planet gears428, 450, through the first-stage and second-stage sun gears 422, 442,and out of the input shaft 410.

As shown, the SAHR clutch assembly 462 includes a SAHR clutch hub 464that is mounted on and engaged for rotation with the first-stage sungear 422. A SAHR clutch flange 466 extends radially outward from theSAHR clutch hub 464 and includes a set of SAHR clutch plates 468 on aradial end. The SAHR clutch plates 468 extend radially outward from theSAHR clutch flange 466 and are positioned in an axial row so as to beinterleaved between the inwardly extending set of plates 415 of theinput shaft clutch element 416. The SAHR clutch assembly 462 furtherincludes a SAHR clutch spring 470 and a SAHR piston 472 that operate toreposition the SAHR clutch assembly 462 between the engaged position andthe disengaged position. During operation, SAHR clutch spring 470functions to urge the SAHR clutch assembly 462 into the engaged positionsuch that the SAHR clutch plates 468 frictionally engage the input shaftclutch element plates 415 of the input shaft clutch element 416, therebylocking the SAHR clutch assembly 462 and the first-stage sun gear 422into rotational engagement with the input shaft clutch element 416 andthe input shaft 410. The SAHR piston 472 is coupled to the SAHR clutchplates 468 and is positioned relative to the input shaft clutch element416 to form a cavity 476. As schematically shown, the cavity 476 isfluidly coupled to a source of fluid pressure, described below. Whenfluid is introduced into the cavity 476, the hydraulic force on the SAHRpiston 472 functions to overcome the force of the SAHR clutch spring 470and urge the SAHR clutch plates 468 out of engagement with the clutchelement plate 415 and into the disengaged position. Subsequently, uponrelease the hydraulic pressure, the SAHR clutch spring 470 repositionsthe SAHR clutch assembly 462 back into the engaged position.

The HASR clutch assembly 478 is formed by a HASR hub 480 that is mountedon and engaged for rotation with the second-stage sun gear 442. A HASRflange 482 extends from the HASR hub 480 and includes inwardly extendingHASR plates 484. The HASR clutch plates 484 extend radially outward fromthe HASR flange 482 and are positioned in an axial row so as to beinterleaved between the outwardly extending set of plates 417 of theinput shaft clutch element 416. The HASR clutch assembly 478 furtherincludes a HASR spring 486 (schematically shown) and HASR piston 488that operate to reposition the HASR clutch assembly 478 between anengaged position and a disengaged position. The HASR clutch spring 486may be arranged in any suitable position, including between the inputshaft clutch element 416 and the HASR clutch plates 484. The HASR piston488 is coupled to the HASR clutch plates 484 and is positioned relativeto the clutch element 416 to form a cavity 490. As schematically shown,the cavity 476 is fluidly coupled to a source of fluid pressure,described below. When fluid is introduced into the cavity 476, the fluidpressure in the cavity 490 operates to overcome the force of the HASRclutch spring 486 and urge the HASR clutch assembly 478 into the engagedposition such that the HASR clutch plates 484 frictionally engage theinput shaft clutch element plates 417 of the input shaft clutch element416, thereby locking the HASR clutch assembly 478 and the second-stagesun gear 442 into rotational engagement with the clutch element 416 andthe input shaft 410. Upon release of the hydraulic pressure in thecavity 490, the HASR clutch spring 486 functions to urge the HASR clutchassembly 478 into the disengaged position such that the HASR clutchplates 484 are separated from the clutch element plates 417, therebyenabling mutually independent rotation of the second-stage sun gear 442and the input shaft 410.

In this implementation, and in contrast to the embodiment of FIG. 4, theSAHR and HASR clutch assemblies 462, 478 of the embodiment of FIG. 9 areoperated with a single control valve 158. As shown, a fluid passage 492is formed in the input shaft clutch element 416, and the fluid passage492 functions to fluidly couple the hydraulic system 152 to the cavities476, 490 via the control valve 158. The fluid passage 492 is formed by acommon branch 494, a SAHR branch 496 extending between the common branch494 and the SAHR cavity 476, and a HASR branch 498 extending between thecommon branch 494 and the HASR cavity 490. The single control valve 158introduces and releases fluid into and out of the fluid passage 492, andthus both cavities 476, 490, in order to actuate the clutch assemblies462, 478, as will be described below.

Reference is made to FIG. 10, which is a partial closer view of thepower transmission assembly 400 during the cold engine start mode; andFIG. 11, which is a partial closer view of the power transmissionassembly 400 during the warm engine start mode. Additional reference ismade to FIG. 12, which is a graph 500 depicting the relationship betweenvalve pressure, clutch torque capacity, and output torque during thecold and warm engine start modes. In particular, valve pressure isreflected on the horizontal axis 502, clutch torque capacity isreflected on the left vertical axis 504, and output torque is reflectedon the right vertical axis 506. As shown in FIG. 12, a first line 510represents the clutch torque capacity of the SAHR clutch assembly 462 inview of valve pressure from the control valve 158; a second line 512represents the clutch torque capacity of the HASR clutch assembly 478 inview of valve pressure from the control valve 158; and a third line 514represents the output torque in view of in view of valve pressure fromthe control valve 158.

The valve pressure at value 520 reflects the position of the controlvalve 158 during the cold engine start mode. As shown, value 520corresponds to a low or “off” valve pressure. At this value 520, theSAHR clutch assembly 462 is engaged as a result of the spring force ofspring 470, as reflected by the relatively high clutch torque capacityof line 510, and the HASR clutch assembly 478 is disengaged as a resultof the spring force of spring 486, as reflected by the relatively lowclutch torque capacity. The positions of the clutch assemblies 462, 478in these positions is depicted in FIG. 10.

In order to transition to the warm engine start mode, the control valve158 increases the valve pressure. As a result of the pressure increase,the clutch torque capacity of the SAHR clutch assembly 462 decreases (asreflected by line 510) and the clutch capacity of the HASR clutchassembly 478 increases (as reflected by line 512). As the HASR clutchassembly 478 engages and the SAHR clutch assembly 462 disengages, thepower flow path of the torque transitions from being transferred throughthe SAHR clutch assembly 462 to being transferring through the HASRclutch assembly 478.

The valve pressure at value 522 reflects the position of the controlvalve 158 during the warm engine start mode. As shown, the value 522corresponds to a high valve pressure. At this value 522, the SAHR clutchassembly 462 is disengaged as a result of fluid pressure, as reflectedby the relatively low clutch torque capacity of line 510, and the HASRclutch assembly 478 is engaged as a result of the fluid pressure, asreflected by the relatively high clutch torque capacity. The positionsof the clutch assemblies 462, 478 in these positions is depicted in FIG.11.

In the generation mode, the engine 120 operates to drive the electricmachine 134 such that the power flows in an opposite direction relativeto the engine start modes. Reference is made to FIG. 13, which is apartial closer view of the power transmission assembly 132 during thegeneration mode. Additional reference is made to FIG. 14, which is agraph 550 depicting the relationship between control valve pressure,clutch torque capacity, and output torque during the generation mode. Inparticular, valve pressure is reflected on the horizontal axis 552,clutch torque capacity is reflected on the left vertical axis 554, andoutput torque is reflected on the right vertical axis 556. As shown inFIG. 14, a first line 560 represents the clutch torque capacity of theSAHR clutch assembly 462 in view of valve pressure from the controlvalve 158, and a second line 562 represents the clutch torque capacityof the HASR clutch assembly 478 in view of valve pressure from thecontrol valve 158. An output torque point 564 represents the outputtorque of the power transmission assembly 132 in view of in view ofvalve pressure from the control valve 158.

As noted above, an increase in valve pressure operates to decrease theclutch torque capacity of the SAHR clutch assembly 462, as reflected byline 552, and to increase the clutch torque capacity of the HASR clutchassembly 478, as reflected by line 554. At an operating point 566 of anintermediate control valve pressure, the SAHR and HASR clutch assemblies462, 478 have balanced clutch torque capacities to result in the outputtorque point 564, which is sufficient to provide the system maximumtorque in the generation mode.

Thus, various embodiments of the vehicle electric system have beendescribed that include an integrated starter-generator device. Varioustransmission assemblies may be included in the device, thus reducing thespace occupied by the system. The transmission assembly may providemultiple speeds or gear ratios and transition between speeds/gearratios. One or more clutch arrangements may be used to selectively applytorque to the gear set of the transmission assembly in both power flowdirections. Direct mechanical engagement with the engine shaft reducesthe complexity and improves reliability of the system. Using planetarygear sets in the transmission assembly provides high gear reduction andtorque capabilities with reduced backlash in a compact space envelope.As a result of the bi-directional nature of the power transmissionassembly, the power transfer belt arrangement may be implemented withonly a single belt tensioner, thereby providing a relatively compact andsimple assembly. Additionally, by using the power transfer beltarrangement with belt and pullies to couple together and transfer powerbetween the electric machine and the power transmission assembly,instead of directly connecting and coupling the electric machine to thepower transmission assembly, the electric machine may be mounted apartfrom the transmission assembly to better fit the engine in a vehicleengine bay. Additionally, by using the belt and pullies to couple theelectric machine to the power transmission assembly, an additional gearratio (e.g., a 4:1 ratio) may be achieved. Embodiments discussed aboveinclude a double planetary gear set, sun in, ring out configuration toprovide warm and cold engine start modes and a ring in, sun outconfiguration to provide a generation mode. As such, a three modeassembly may be provided. Control of the gear set may be implementedwith dedicated control valves or a single control valve.

Also, the following examples are provided, which are numbered for easierreference.

1. A power control system for a work vehicle with an engine, the powercontrol system comprising: a combination starter-generator device,having: an electric machine; a gear set configured to receive rotationalinput from the electric machine and from the engine and to couple theelectric machine and the engine in a first power flow direction and asecond power flow direction, the gear set configured to operate in oneof multiple relatively high-torque, low-speed start gear ratios in thefirst power flow direction, including a first start gear ratiocorresponding to a cold engine start mode and a second start gear ratiocorresponding to a warm engine start mode, the gear set furtherconfigured to operate in a relatively low-torque, high-speed gear ratioin the second power flow direction corresponding to a generation mode;and a first clutch assembly and a second clutch assembly selectivelycoupled to the gear set to effect the first start gear ratio during thecold engine start mode and the second start gear ratio during the warmengine start mode; and a control valve fluidly coupled to selectivelyapply a fluid pressure to the first clutch assembly and to the secondclutch assembly.

2. The power control system of example 1, wherein the control valve is asingle solenoid valve.

3. The power control system of example 1, wherein the first clutchassembly is engaged during the cold engine start mode to result in thegear set operating according to the first start gear ratio, disengagedduring the warm engine start mode to result in the gear set operatingaccording to the second start gear ratio, and engaged in the secondpower flow direction; and wherein the second clutch assembly isdisengaged during the cold engine start mode to result in the gear setoperating according to the first start gear ratio, engaged during thewarm engine start mode to result in the gear set operating according tothe second start gear ratio, and engaged in the second power flowdirection.

4. The power control system of example 1, further comprising acontroller configured to generate command signals to the control valveto selectively actuate the first clutch assembly between a first engagedposition and a first disengaged position and to selectively actuate thesecond clutch assembly between a second engaged position and a seconddisengaged position.

5. The power control system of example 4, wherein the controller, in thecold engine start mode, is configured to generate the command signalsfor the control valve such that the first clutch assembly is in thefirst engaged position and the second clutch assembly is in the seconddisengaged position, wherein the controller, in the warm engine startmode, is configured to generate the command signals for the controlvalve such that the first clutch assembly is in the first disengagedposition and the second clutch assembly is in the second engagedposition, and wherein the controller, in the generation mode, isconfigured to generate the command signals for the control valve suchthat the first clutch assembly is in the first engaged position and thesecond clutch assembly is in the second engaged position.

6. The power control system of example 5, wherein the controller, in thecold engine start mode, is configured to generate the command signalsfor the control valve to apply a first fluid pressure value, wherein thecontroller, in the warm engine start mode, is configured to generate thecommand signals for the control valve to apply a second fluid pressurevalue, greater than the first fluid pressure value, and wherein thecontroller, in the generation mode, is configured to generate thecommand signals for the control valve to apply a third fluid pressurevalue, in between the first fluid pressure value and the second fluidpressure value.

7. The power control system of example 6, wherein the first clutchassembly includes a first spring configured to urge the first clutchassembly into the first engaged position and a first piston proximate toa first cavity that, when supplied with fluid pressure, resists thefirst spring and urges the first clutch assembly into the firstdisengaged position, wherein the second clutch assembly includes asecond spring configured to urge the second clutch assembly into thesecond disengaged position and a second piston proximate to a secondcavity that, when supplied with fluid pressure, resists the secondspring and urges the second clutch assembly into the second engagedposition, and wherein the combination starter-generator device furthercomprises a fluid passage that fluidly couples the control valve to thefirst cavity and the second cavity.

8. The power control system of example 7, wherein the fluid passage isformed by a common branch fluidly coupled to the control valve, a firstbranch extending between the common branch and the first cavity, and asecond branch extending between the common branch and the second cavity.

9. The power control system of example 1, wherein the gear set isbi-directional in that, in the first power flow direction, the gear setreceives input power from the electric machine in a first clockdirection and outputs power to the engine in a second clock directionopposite the first clock direction; and wherein, in the second powerflow direction, input power from the engine is in the second clockdirection and output power to the electric machine is in the secondclock direction.

10. The power control system of example 9, further including a belt andpulley coupled to the gear set and the electric machine, wherein inputpower in the first power flow direction is conveyed from the electricmachine to the gear set by the belt and pulley, and wherein in the firstpower flow direction the belt and pulley rotate in the first clockdirection and in the second power flow direction the belt and pulleyrotate in the second clock direction.

11. The power control system of example 10, further including a singlebelt tensioner applying tension to a first side of the belt in both thefirst power direction and the second power flow direction.

12. The power control system of example 1, wherein the starter-generatordevice further includes a third clutch assembly that is engaged duringthe first start gear ratio and the second start gear ratio anddisengaged in second power flow direction.

13. The power control system of example 12, wherein the third clutchassembly is a one-way mechanically-actuated clutch.

14. The power control system of example 1, wherein the gear set includesa compound epicyclic gear train including first-stage and second-stagesun gears, first-stage and second-stage planet gears, first-stage andsecond-stage carriers, and a ring gear; and wherein the first-stageplanet gears have a different tooth count than the second-stage planetgears.

15. The power control system of example 14, wherein rotational powerfrom the electric machine moves in the first power flow direction fromthe first-stage sun gear to the ring gear to the engine, and whereinrotational power from the engine moves in the second power flowdirection from the ring gear to the first-stage sun gear to the electricmachine, and wherein the combination starter-generator device furtherincludes a third clutch assembly coupled to the gear set and disposedbetween the engine and the electric machine, and wherein the thirdclutch assembly is configured to engage during the first start gearratio and the second start gear ratio to couple the second-stage carrierto a housing of the gear set and to disengage in the second power flowdirection to uncouple the second-stage carrier from the housing of thegear set.

As will be appreciated by one skilled in the art, certain aspects of thedisclosed subject matter can be embodied as a method, system (e.g., awork vehicle control system included in a work vehicle), or computerprogram product. Accordingly, certain embodiments can be implementedentirely as hardware, entirely as software (including firmware, residentsoftware, micro-code, etc.) or as a combination of software and hardware(and other) aspects. Furthermore, certain embodiments can take the formof a computer program product on a computer-usable storage medium havingcomputer-usable program code embodied in the medium.

Any suitable computer usable or computer readable medium can beutilized. The computer usable medium can be a computer readable signalmedium or a computer readable storage medium. A computer-usable, orcomputer-readable, storage medium (including a storage device associatedwith a computing device or client electronic device) can be, forexample, but is not limited to, an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system, apparatus, ordevice, or any suitable combination of the foregoing. More specificexamples (a non-exhaustive list) of the computer-readable medium wouldinclude the following: an electrical connection having one or morewires, a portable computer diskette, a hard disk, a random-access memory(RAM), a read-only memory (ROM), an erasable programmable read-onlymemory (EPROM or Flash memory), an optical fiber, a portable compactdisc read-only memory (CD-ROM), an optical storage device. In thecontext of this document, a computer-usable, or computer-readable,storage medium can be any tangible medium that can contain, or store aprogram for use by or in connection with the instruction executionsystem, apparatus, or device.

A computer readable signal medium can include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal can takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium can be non-transitory and can be anycomputer readable medium that is not a computer readable storage mediumand that can communicate, propagate, or transport a program for use byor in connection with an instruction execution system, apparatus, ordevice.

Aspects of certain embodiments are described herein can be describedwith reference to flowchart illustrations and/or block diagrams ofmethods, apparatus (systems) and computer program products according toembodiments of the disclosure. It will be understood that each block ofany such flowchart illustrations and/or block diagrams, and combinationsof blocks in such flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions can be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions can also be stored in acomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions can also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions which execute on the computer or other programmableapparatus provide steps for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

Any flowchart and block diagrams in the figures, or similar discussionabove, can illustrate the architecture, functionality, and operation ofpossible implementations of systems, methods and computer programproducts according to various embodiments of the present disclosure. Inthis regard, each block in the flowchart or block diagrams can representa module, segment, or portion of code, which includes one or moreexecutable instructions for implementing the specified logicalfunction(s). It should also be noted that, in some alternativeimplementations, the functions noted in the block (or otherwisedescribed herein) can occur out of the order noted in the figures. Forexample, two blocks shown in succession (or two operations described insuccession) can, in fact, be executed substantially concurrently, or theblocks (or operations) can sometimes be executed in the reverse order,depending upon the functionality involved. It will also be noted thateach block of any block diagram and/or flowchart illustration, andcombinations of blocks in any block diagrams and/or flowchartillustrations, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The description of the present disclosure has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the disclosure in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of thedisclosure. Explicitly referenced embodiments herein were chosen anddescribed in order to best explain the principles of the disclosure andtheir practical application, and to enable others of ordinary skill inthe art to understand the disclosure and recognize many alternatives,modifications, and variations on the described example(s). Accordingly,various embodiments and implementations other than those explicitlydescribed are within the scope of the following claims.

What is claimed is:
 1. A power control system for a work vehicle with anengine, the power control system comprising: a combinationstarter-generator device, having: an electric machine; a gear setconfigured to receive rotational input from the electric machine andfrom the engine and to couple the electric machine and the engine in afirst power flow direction and a second power flow direction, the gearset configured to operate in one of multiple relatively high-torque,low-speed start gear ratios in the first power flow direction, includinga first start gear ratio corresponding to a cold engine start mode and asecond start gear ratio corresponding to a warm engine start mode, thegear set further configured to operate in a relatively low-torque,high-speed gear ratio in the second power flow direction correspondingto a generation mode; and a first clutch assembly and a second clutchassembly selectively coupled to the gear set to effect the first startgear ratio during the cold engine start mode and the second start gearratio during the warm engine start mode; and a control valve fluidlycoupled to selectively apply a fluid pressure to the first clutchassembly and to the second clutch assembly.
 2. The power control systemof claim 1, wherein the control valve is a single solenoid valve.
 3. Thepower control system of claim 1, wherein the first clutch assembly isengaged during the cold engine start mode to result in the gear setoperating according to the first start gear ratio, disengaged during thewarm engine start mode to result in the gear set operating according tothe second start gear ratio, and engaged in the second power flowdirection; and wherein the second clutch assembly is disengaged duringthe cold engine start mode to result in the gear set operating accordingto the first start gear ratio, engaged during the warm engine start modeto result in the gear set operating according to the second start gearratio, and engaged in the second power flow direction.
 4. The powercontrol system of claim 1, further comprising a controller configured togenerate command signals to the control valve to selectively actuate thefirst clutch assembly between a first engaged position and a firstdisengaged position and to selectively actuate the second clutchassembly between a second engaged position and a second disengagedposition.
 5. The power control system of claim 4, wherein thecontroller, in the cold engine start mode, is configured to generate thecommand signals for the control valve such that the first clutchassembly is in the first engaged position and the second clutch assemblyis in the second disengaged position, wherein the controller, in thewarm engine start mode, is configured to generate the command signalsfor the control valve such that the first clutch assembly is in thefirst disengaged position and the second clutch assembly is in thesecond engaged position, and wherein the controller, in the generationmode, is configured to generate the command signals for the controlvalve such that the first clutch assembly is in the first engagedposition and the second clutch assembly is in the second engagedposition.
 6. The power control system of claim 5, wherein thecontroller, in the cold engine start mode, is configured to generate thecommand signals for the control valve to apply a first fluid pressurevalue, wherein the controller, in the warm engine start mode, isconfigured to generate the command signals for the control valve toapply a second fluid pressure value, greater than the first fluidpressure value, and wherein the controller, in the generation mode, isconfigured to generate the command signals for the control valve toapply a third fluid pressure value, in between the first fluid pressurevalue and the second fluid pressure value.
 7. The power control systemof claim 6, wherein the first clutch assembly includes a first springconfigured to urge the first clutch assembly into the first engagedposition and a first piston proximate to a first cavity that, whensupplied with fluid pressure, resists the first spring and urges thefirst clutch assembly into the first disengaged position, wherein thesecond clutch assembly includes a second spring configured to urge thesecond clutch assembly into the second disengaged position and a secondpiston proximate to a second cavity that, when supplied with fluidpressure, resists the second spring and urges the second clutch assemblyinto the second engaged position, and wherein the combinationstarter-generator device further comprises a fluid passage that fluidlycouples the control valve to the first cavity and the second cavity. 8.The power control system of claim 7, wherein the fluid passage is formedby a common branch fluidly coupled to the control valve, a first branchextending between the common branch and the first cavity, and a secondbranch extending between the common branch and the second cavity.
 9. Thepower control system of claim 1, wherein the gear set is bi-directionalin that, in the first power flow direction, the gear set receives inputpower from the electric machine in a first clock direction and outputspower to the engine in a second clock direction opposite the first clockdirection; and wherein, in the second power flow direction, input powerfrom the engine is in the second clock direction and output power to theelectric machine is in the second clock direction.
 10. The power controlsystem of claim 9, further including a belt and pulley coupled to thegear set and the electric machine, wherein input power in the firstpower flow direction is conveyed from the electric machine to the gearset by the belt and pulley, and wherein in the first power flowdirection the belt and pulley rotate in the first clock direction and inthe second power flow direction the belt and pulley rotate in the secondclock direction.
 11. The power control system of claim 10, furtherincluding a single belt tensioner applying tension to a first side ofthe belt in both the first power direction and the second power flowdirection.
 12. The power control system of claim 1, wherein thestarter-generator device further includes a third clutch assembly thatis engaged during the first start gear ratio and the second start gearratio and disengaged in second power flow direction.
 13. The powercontrol system of claim 12, wherein the third clutch assembly is aone-way mechanically-actuated clutch.
 14. The power control system ofclaim 1, wherein the gear set includes a compound epicyclic gear trainincluding first-stage and second-stage sun gears, first-stage andsecond-stage planet gears, first-stage and second-stage carriers, and aring gear; and wherein the first-stage planet gears have a differenttooth count than the second-stage planet gears.
 15. The power controlsystem of claim 14, wherein rotational power from the electric machinemoves in the first power flow direction from the first-stage sun gear tothe ring gear to the engine, and wherein rotational power from theengine moves in the second power flow direction from the ring gear tothe first-stage sun gear to the electric machine.
 16. The power controlsystem of claim 15, wherein the combination starter-generator devicefurther includes a third clutch assembly coupled to the gear set anddisposed between the engine and the electric machine, and wherein thethird clutch assembly is configured to engage during the first startgear ratio and the second start gear ratio to couple the second-stagecarrier to a housing of the gear set and to disengage in the secondpower flow direction to uncouple the second-stage carrier from thehousing of the gear set.
 17. The power control system of claim 16,wherein the third clutch assembly is a one-way mechanically-actuatedclutch.
 18. A power system for a work vehicle, comprising: an engine; anelectric machine; a combination starter-generator device, having: a gearset configured to receive rotational input from the electric machine andfrom the engine and to couple the electric machine and the engine in afirst power flow direction and a second power flow direction, the gearset configured to operate in one of multiple relatively high-torque,low-speed start gear ratios in the first power flow direction, includinga first start gear ratio corresponding to a cold engine start mode and asecond start gear ratio corresponding to a warm engine start mode, thegear set further configured to operate in a relatively low-torque,high-speed gear ratio in the second power flow direction correspondingto a generation mode; a first clutch assembly coupled to the gear set,wherein the first clutch assembly is engaged during the cold enginestart mode to result in the gear set operating according to the firststart gear ratio, disengaged during the warm engine start mode to resultin the gear set operating according to the second start gear ratio, andengaged in the second power flow direction; a second clutch assemblycoupled to the gear set, wherein the second clutch assembly isdisengaged during the cold engine start mode to result in the gear setoperating according to the first start gear ratio, engaged during thewarm engine start mode to result in the gear set operating according tothe second start gear ratio, and engaged in the second power flowdirection; and a third clutch assembly that is engaged in first powerflow direction during the cold engine start mode and the warm enginestart mode and is disengaged in second power flow direction during thegeneration mode; and a single control valve fluidly coupled toselectively apply a fluid pressure to the first clutch assembly and tothe second clutch assembly.
 19. The power system of claim 18, furthercomprising a controller configured to generate command signals for thecontrol valve to selectively actuate the first clutch assembly between afirst engaged position and a first disengaged position and toselectively actuate the second clutch assembly between a second engagedposition and a second disengaged position, wherein the controller, inthe cold engine start mode, is configured to generate the commandsignals for the control valve to apply a first fluid pressure value suchthat the first clutch assembly is in the first engaged position and thesecond clutch assembly is in the second disengaged position, wherein thecontroller, in the warm engine start mode, is configured to generate thecommand signals for the control valve to apply a second fluid pressurevalue such that the first clutch assembly is in the first disengagedposition and the second clutch assembly is in the second engagedposition, the second fluid pressure value being greater than the firstfluid pressure value, and wherein the controller, in the generationmode, is configured to generate the command signals for the controlvalve to apply a third fluid pressure value such that the first clutchassembly is in the first engaged position and the second clutch assemblyis in the second engaged position, the third fluid pressure value beingin between the first fluid pressure value and the second fluid pressurevalue.
 20. The power system of claim 19, wherein the gear set includes acompound epicyclic gear train including first-stage and second-stage sungears, first-stage and second-stage planet gears, first-stage andsecond-stage carriers, and a ring gear; wherein the first-stage planetgears have a different tooth count than the second-stage planet gears;and wherein rotational power from the electric machine moves in thefirst power flow direction from the first-stage sun gear to the ringgear to the engine, and rotational power from the engine moves in thesecond power flow direction from the ring gear to the first-stage sungear to the electric machine; wherein the combination starter-generatordevice further includes a third clutch assembly coupled to the gear setand disposed between the engine and the electric machine; wherein thefirst clutch assembly is configured to engage during the first startgear ratio and in the second power flow direction to couple thefirst-stage sun gear to an input member coupled to the electric machineand to disengage during the second start gear ratio to uncouple thefirst-stage sun gear from the input member; wherein the second clutchassembly is configured to disengage during the first start gear ratio touncouple the second-stage sun gear from the input member and to engageduring the second start gear ratio and in the second power flowdirection to couple the second-stage sun gear to the input member; andwherein the third clutch assembly is configured to engage during thefirst start gear ratio and the second start gear ratio to couple thesecond-stage carrier to a housing of the gear set and to disengage inthe second power flow direction to uncouple the second-stage carrierfrom the housing of the gear set.